Continuous melatonin administration accelerates resynchronization following phase shifts of a light-dark cycle

Hau, Michaela

doi:10.1016/0031-9384(95)00002-z

Cited by 33 publications

(15 citation statements)

References 53 publications

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“…Implants similar to those used in our experiment are known to dampen behavioural circadian rhythmicity in laboratory housed songbirds [4]. In this study, however, melatonin treatment did not alter the timing of daily activity onset (see electronic supplementary material); unlike the delay in activity onset observed in laboratory male songbirds when treated similarly with melatonin [26]. This observation renders it unlikely that the delay of clutch initiation was due to an effect of melatonin on the circadian system, although at present we cannot fully exclude this idea.…”

Section: Discussionmentioning

confidence: 49%

Melatonin delays clutch initiation in a wild songbird

et al. 2011

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The hormone melatonin is known to play an important role in regulating many seasonal changes in physiology, morphology and behaviour. In birds, unlike in mammals, melatonin has thus far been thought to play little role in timing seasonal reproductive processes. This view is mainly derived from laboratory experiments on male birds. This study tests whether melatonin is capable of influencing the timing of clutch initiation in wild female songbirds. Free-living female great tits (Parus major) treated with melatonin-filled implants prior to the breeding season initiated their first clutch of the season significantly later than females carrying an empty implant. Melatonin treatment did not affect clutch size. Further, melatonin treatment did not delay the onset of daily activity in the wild nor adversely affect body mass in captivity compared with controls. These data suggest a previously unknown role for this hormone in regulating the timing of clutch initiation in the wild.

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Section: Discussionmentioning

confidence: 49%

Melatonin delays clutch initiation in a wild songbird

et al. 2011

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“…Thus for black-headed gulls it makes sense to physiologically signal the night as a time when little or no activity will take place-a task generally ascribed to the increase in plasma melatonin in day-active birds [26]. On the other hand, we suggest that the main physiological reason for tonically low melatonin levels in swallow-tailed gulls is to keep their circadian pacemaker less self-sustained [7,8,13,14]. A poorly self-sustained pacemaker would allow the animals to be active intermittently and potentially also permit an easier or faster synchronization with tidal or moonlight patterns, which could be important determinants of (nocturnal) foraging times in seabirds [27].…”

Section: Discussionmentioning

confidence: 98%

“…The only exceptions are owl species, such as the nocturnal barn owl [Tyto alba; 11], which may have low nocturnal melatonin levels as a prerequisite for activity at night. We hypothesize, following Gwinner et al [8], that, in general, melatonin lacks a diel rhythm in bird species that have the challenge of being active during the night and also intermittently during the day [12][13][14][15]. To address this hypothesis we compare melatonin concentrations in a nocturnal-foraging and a diurnal gull species.…”

Section: Introductionmentioning

confidence: 96%

Do night-active birds lack daily melatonin rhythms? A case study comparing a diurnal and a nocturnal-foraging gull species

et al. 2006

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Plasma melatonin concentrations in most animals investigated so far increase at night regardless of whether individuals are day or night active. Nevertheless, daily melatonin amplitudes are often seasonally adjusted to ecological conditions, with birds that breed at high latitudes and migrate during the night showing lower daily amplitudes. Here we investigate whether nocturnal seabirds, gulls that feed at night, also show a low melatonin amplitude because they have to be active predominantly during the night but also intermittently during the day. We sampled free-living nocturnal-foraging swallow-tailed gulls (Creagrus furcatus) on two Galapagos islands every $4 h and compared their plasma melatonin concentrations with those of related black-headed gulls (Larus ridibundus) sampled in the Netherlands. Like most seabirds, the black-headed gulls showed generally low melatonin concentrations, but clear diel cycles. The swallow-tailed gulls, on the other hand, had similarly low absolute melatonin concentrations, but no detectable diel changes. Despite problems inherent in comparisons between two species and field/ lab setups, our data lend support to the hypothesis that the lack of a diel melatonin rhythm allows animals to be active at any time.

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“…Three previous studies that attempted to test this hypothesis used an approach where endogenous melatonin rhythm was eliminated by "covering" it with high levels of melatonin supplied through subcutaneous silastic implants (Hau and Gwinner 1995;Pohl 1996;Abraham et al 2000). Although results from these studies showed acceleration of resynchronization after phase shifts of photic (Hau and Gwinner 1995) and nonphotic zeitgebers, it remained unclear whether the effects produced were due to the absence of rhythmic pineal melatonin or due to the presence of supraphysiological levels of melatonin (>100 times of the normal nighttime melatonin levels, Abraham et al 2000). In any case, the elimination of rhythmicity in blood melatonin by exogenous melatonin is not equivalent to the absence of pineal melatonin rhythm.…”

Section: Introductionmentioning

confidence: 99%

Pinealectomy shortens resynchronisation times of house sparrow (Passer domesticus) circadian rhythms

Kumar

Gwinner

2005

Naturwissenschaften

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In many birds periodic melatonin secretion by the pineal organ is essential for the high-amplitude self-sustained output of the circadian pacemaker, and thus for the persistence of rhythmicity in 24 h oscillations controlled by it. The elimination of the pineal melatonin rhythm, or a reduction of its amplitude, renders the circadian pacemaker a less self-sustained, often highly damped, oscillatory system. A reduction in the degree of self-sustainment of a rhythm should not only increase its range of entrainment but also shorten the resynchronization times following phase-shifts of the zeitgeber. This hypothesis has not yet been directly tested. We therefore carried out the present study in which house sparrows (Passer domesticus) were subjected to both 6-h advance and 6-h delay phase-shifts of the light-dark cycle before and after the pinealectomy, and the rhythms in locomotion and feeding were recorded. The results indicate that following the delay, but not the advance, phase shift, resynchronization times were significantly shorter after pinealectomy. The dependence of resynchronization times on the presence or absence of the pineal organ is not only of theoretical interest but might also be of functional significance in the natural life of birds. A reduction or elimination of the amplitude of the melatonin secretion rhythm by the pineal organ might be responsible for faster adjustment to changes in zeitgeber conditions in nature.

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Continuous melatonin administration accelerates resynchronization following phase shifts of a light-dark cycle

Cited by 33 publications

References 53 publications

Melatonin delays clutch initiation in a wild songbird

Melatonin delays clutch initiation in a wild songbird

Do night-active birds lack daily melatonin rhythms? A case study comparing a diurnal and a nocturnal-foraging gull species

Pinealectomy shortens resynchronisation times of house sparrow (Passer domesticus) circadian rhythms

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